The present invention relates to a drive system for wire rope hoists.
In a conventional traction drive arrangement for wire rope hoists the rope tension over the drive sheave is obtained due to the fact that the ropes at one end carry the weight of the hoist cage plus load and at the other end carry a counterweight.
The drive sheave then transfers a force that essentially corresponds to the weight difference between either the hoist cage plus load and the counterweight or the counterweight and the empty hoist cage. Also the weight of the ropes affects said force if there are no "compensation" ropes. The weight of the ropes thus reduces the load capacity and becomes an increasing problem at increasing host system heights. As a remedy it is conventional at high hoist system heights to compensate for this "rope unbalance", i.e. the weight of ropes, by hanging "compensation" ropes with a corresponding weight below and between the hoist cage and the counterweight.
One object of the present invention is to eliminate the needs of a counterweight and of compensation for the "rope unbalance".